A cochlear implant (CI) is a neural prosthetic device that restores hearing by directly stimulating the auditory nerve using an electrode array that is surgically implanted in the cochlea (U.S. Food and Drug Administration, 1995). An external sound processor, typically worn behind the ear, processes sounds detected by a microphone into signals sent to the implanted electrodes. The CI sound processor is programmed after implantation by an audiologist. Based on patient response, the audiologist determines stimulation levels for each electrode and selects a frequency allocation table to define which electrodes should be activated when specific sound frequencies are detected (Wilson et al., 1991). The number of electrodes in a CI electrode array ranges from 12 to 22, depending on the manufacturer.
CI electrode arrays are designed such that when optimally placed in the scala tympani cavity of the cochlea, each electrode stimulates regions of the auditory nerve corresponding to a pre-defined frequency bandwidth (Wilson et al., 2008). However, because the surgeon threads the electrode array blind to internal cavities of the cochlea during the surgery, the final position of the electrode array relative to intra-cochlear anatomy is generally unknown. Research has shown that in 73% of CI surgeries the electrode array is placed fully within the scala tympani, while in the other 27% of CI surgeries, the electrode array is fully within a neighboring cavity or is initially inserted into the scala tympani but crosses into a neighboring cavity (Aschendorff et al., 2007). So far, the only option when programming the CI has been to assume the array is optimally placed in the cochlea and to use a default frequency allocation table. However, interpretation error in the locations of the CI device often occurs, resulting in poor programming of the CI and un-optimized sound effect.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.